In an engine generator that generates power using a generator driven by an engine, an engine rotational number (engine rotational speed) varies according to a change in a load during autonomous operation. Thus, an allowable rotational speed range (allowable speed change range) is generally predetermined for the engine. The engine generator operates unstably when the engine rotational speed deviates from the allowable engine rotational speed range. For example, when a load is once cut off for some reason and then is re-applied, it is necessary to consider the allowable engine rotational speed range for applying the load. Accordingly, in the engine generator, the amount of load that can be applied is limited.
In this regard, Patent Document 1 discloses a configuration in which power storage means (power storage device) including a capacitor and the like is provided in a path on the DC side from a generator to an inverter so as to address the change in the load by discharge of the power storage means while operating the generator constantly at the maximum efficiency point. Thus, the change in the engine rotational speed is suppressed.